Figure 2.

Efficiency of B cell lysis by type I monoclonal antibody (mAb) as compared with type II mAb and with anti‐CD22 mAb. A, Whole blood samples were incubated with or without 1 μg/ml of either rituximab (RTX; IgG1), ofatumumab (2F2; IgG1), tositumomab (B1; mouse IgG2a), or glycosylated GA101 with an unmodified Fc portion (GA101_Gly; IgG1). After 24 hours, the percentage of B cell death was measured by flow cytometry. The cytotoxicity of type I and type II mAb was compared in patients with rheumatoid arthritis (n = 3) and systemic lupus erythematosus (SLE; n = 10). Type I mAb lysed B cells less efficiently than did type II mAb, with a cytotoxicity index for RTX < 2F2 < B1 < GA101_Gly. Values are the mean of triplicate wells. Each line represents an individual sample. B, In SLE patients (n = 4), the cytotoxicity index of anti‐CD22mAb was significantly lower than that of RTX and GA101_Gly. ∗ = P < 0.05; ∗∗ = P < 0.005; ∗∗∗ = P < 0.0001.